1. Field of the Invention
This invention generally relates to phase-locked loops (PLLs) and, more particularly, to a system and method for adaptively calibrating a multi-band PLL.
2. Description of the Related Art
Generally, Process, Voltage, Temperature (PVT) is understood to be a relationship between two or more functions associated with matter. Electronic circuitry, especially nanometer technology, is very sensitive to PVT variations. Since the effect of PVT variations is unknown, device performance can be uncertain in response to real-time on-chip variations. Process variations occur because of imperfect fabrication processes that cause integrated circuits (IC) to exhibit different delay or frequency shifts than intended during design. IC process variations for a device result in different functional behaviors from chip-to-chip.
A multi-band PLL is intended to operate over an extremely broad range of frequencies. Several voltage controlled oscillators (VCOs) may be required if the frequency range is very broad. In that case, the range is segmented into a series of adjacent frequency bands, where each frequency band is associated with a corresponding VCO. In the case of such a multi-band PLL device, PVT variations can result in frequency band shifts between devices, requiring customer support as the device VCOs and frequency bands require case-by-case custom tuning and realignment.
It would be advantageous if a multi-band PLL could be recalibrated on-the-fly, to realign VCOs with frequency bands, accommodating unforeseen changes due to the effects of PVT.